/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.jooby.internal;

import static java.util.Objects.requireNonNull;

import java.time.Instant;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.util.Calendar;
import java.util.Date;
import java.util.Locale;

public class Headers {

  public static final DateTimeFormatter fmt = DateTimeFormatter
      .ofPattern("EEE, dd MMM yyyy HH:mm:ss z", Locale.ENGLISH)
      .withZone(ZoneId.of("GMT"));

  public static String encode(final Object value) {
    requireNonNull(value, "Header value is required.");
    if (value instanceof Date) {
      return fmt.format(Instant.ofEpochMilli(((Date) value).getTime()));
    }
    if (value instanceof Calendar) {
      return fmt.format(Instant.ofEpochMilli(((Calendar) value).getTimeInMillis()));
    }
    return value.toString();
  }

}
